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Homework Help: Velocity, Acceleration, Car problem

  1. Sep 8, 2009 #1
    1. The problem statement, all variables and given/known data
    A car accelerates at 2.0 m/s^2 along a straight road. It passes two marks that are 30 m apart at times t = 4.0s and t = 5.0s. What was the car's velocity at t = 0s?

    2. Relevant equations

    There are some equations in the chapter that I have used for previous homework problems but for this one I'm not sure which one or ones to use.

    (Vf)^2 = (Vi)^2 + 2ad
    (d = distance)
    a = vf - vi/t
    d = vt + 1/2a(t)^2

    3. The attempt at a solution

    I have tried finding the initial velocity at t = 0s but I can't seem to find a way to utilize the other variables.


  2. jcsd
  3. Sep 8, 2009 #2


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    Homework Helper

    Using the first equation, find vf^2 - vi^2.
    Using second equation find vf - vi.
    From these two equations, find vf + vi.
    Solve the above two equations to get vi and vf.
    Here vi is the velocity a the end of 4 second, From that you can find v0 at t = 0
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